Fluorinated without additives

On the other hand, the fluorine-induced addition of the diastereomeric silyl-subsliluted sulfides 36 A and 36B to benzaldehyde proceeds without loss of stereochemical information and with retention of configuration32. Since, however, the anionic reagent 35A/35B is known to be configurationally labile, the observed retention of configuration in the fluorine-induced desi-lylative hydroxy alkylation lends experimental evidence to the notion that these reactions proceed via hypervalent silicon species rather than anionic reagents. 

There are no reports of fluorination of acetophenone, but 2,2,2-trifluoro-t-phenylethanone and its homologs react with sulfur tetrafluoride at 100 150°C, even without addition of hydrogen fluoride, to give reasonable to good yields of fluoroalkylbenzcncs l.51... 

Thus, the reaction of 1,4-dioxane with sulfur tetrafluoride and hydrogen fluoride in the presence of small amounts of sulfur chlorides or chlorine (0.3 0.5 %) at 185-220°C results in the replacement of 3-5 hydrogen atoms by fluorine to give mixtures of a polyfluoro-1,4-dioxane 1 or 3 and 2-fluoroethyl-l,2,2,2-tetrafluoroethyl ether (2) in a ratio dependent on the reaction temperature.237 Using technical grade sulfur tetrafluoride without addition of a sulfur chloride or chlorine, this reaction is not reproducible, but when carefully purified sulfur tetrafluoride is used the reaction does not give fluorinated products, instead a tar is formed.237... 

Treatment of cholesterol or pregnolone acetate with excess lead(IV) acetate and anhydrous hydrogen fluoride in dry dichloromethane at — 70r C results in controlled cist addition of fluorine without ring contraction to give 5a,6a-difluorocholestan-3j8-ol and 5a,6c<-difluoro-3/J-hy-droxypregnan-20-one in 28 and 27% yield, respectively.25,26... 

For exchange of tertiary alcohols direct fluorination without activation can be achieved by use of aHF or other sources of acidic fluoride (Scheme 2.61). This type of reaction in an acidic medium proceeds via a stabilized carbocation by an Sjjl mechanism. Fluoride addition is often reversible, and the stereochemistry of the reaction is controlled thermodynamically only by the relative free enthalpies of the possible product isomers. 

A small sintered alumina vessel containii IifeOb is fluorinated in a quartz tube (in an apparatus similar to that used for the preparation of TIF3). After gentle initial heating, the reaction proceeds (occasionally with incandescence) without additional supply of heat. The progress of the conversion may be checked since the yellow oxide becomes colorless and an increase in volume takes place simviltaneously. To obtain a completely oxide-free preparation the product must be kept for several hours at 500°C in a nickel tube, while a stream of fluorine is passed over it. 

Defluorination of fluoroapatite in arc discharges without additives can exceed 90% at temperatures above 2000 K. The decomposition (7-111) leads to formation of solid products. Defluorination can be easier to do when fluorine is fixed in products in the gas phase. Such processes are conducted in the presence of Si02. Plasma defluorination leads to the formation of tricalcium phosphate with fluorine in gaseous S1F4,... 

Viscoelastic Worm-Like Micelles in Nonionic Fluorinated Suifrictant System (Without Additives)... 

Oxidation of 3-methyltetrafluoroindoles 178 by selenium dioxide in presence of acetic anhydride can be stopped at the alcohol oxidation level step to give acetates 179. Fluorinated 3-indolylcarbaldehydes 180 were isolated in high yields when the oxidation was performed without addition of acetic anhydride [54], Further oxidation of aldehyde was achieved by treatment with potassium permanganate to afford 3-indolylcarboxylic acid 181 in high yield [58c],... 

It is more reactive than perchloryl fluoride and therefore not without danger. It forms, for instance, a highly explosive product with pyridine. Like perchloryl fluoride it reacts with enol ethers, esters and enamines, but at lower temperature (—78°) to yield the fluorinated ketones as well as addition... 

DUPLEX Disks extend corrosion resistance to highly oxidizing agents, halogens except free fluorine, and virtually all other corrosives. A sheet of PIPE is used as a barrier on the service side of the disk. See page 12. Additionally, these disks are processed to accommodate temperatures to 392E without insulation. 

---